http://onestepback.org/index.cgi/Tech/Ruby/WEBrick.rdoc with a change to use /usr/bin/env ruby instead of /usr/local/bin/ruby

servefiles.rb

#!/usr/bin/env ruby
require 'webrick'
include WEBrick

dir = Dir::pwd
port = 12000 + (dir.hash % 1000)

url = "http://#{Socket.gethostname}:#{port}"

puts "URL: #{url}"

s = HTTPServer.new(
  :Port            => port,
  :DocumentRoot    => dir
)

trap("INT"){ s.shutdown }
s.start